Expulsion-bag tank for liquid propellant



April 18, 1961 w. J. GLASSON EXPULSIONBAG TANK FOR LIQUID PROPELLANTFiled Aug. 15, 1957 [WA/70K United States Patent EXPULSION-BAG TANK FORLIQUID PROPELLANT William J. Glasson, Los Angeles, Calif., assignor toHughes Aircraft Company, Culver City, Cahf., a corporation of DelawareFiled Aug. 15, 1957, Ser. No. 678,760

1 Claim. (Cl. 158-501) This invention relates to storage and deliverymeans for liquid fuels, and particularly to means for retaining andfurnishing such fuels at relatively high pressures.

The invention is directly concerned with retaining a liquid propellant,such as ethylene oxide, in a tank under pressure until it is to beconsumed, and then forcing it into the motor means almostinstantaneously, The problem is of particular concern in devices such asrockets and guided missiles, in which the special fuel components mustbe supplied with great rapidity on demand. It is necessary to deliverthe fuel under high pressures in order to meet the need for rapiddelivery of power, and it is necessary that the propellant stay underpressures at all times. It is also necessary to deliver the fuel in adesired direction on demand. Since the attitude of the device and thedirection of the accelerating forces to which it may be subjected atthat time cannot be predicted in advance, a separator is requiredbetween the propellant and the pressurizing gas to insure that theformer is expelled in the proper direction from its placeof storagethrough the proper delivery conduit. However, 'it has been found that acommonly used propellant material,

ethylene oxide, deteriorates all presently known flexible materialspractical for use as a bladder or separator to contain and assist inexpelling the fluid. Most other inert sealing materials are not suitablefor insuring that a good seal is maintained.

Other approaches in the prior art have included-the use of a pistonbetween the pressurized gas and the propellant. This requires that agood seal be maintained about the periphery of the piston, which seal,again, may be subject to deterioration by the propellant, so that it mayfail when the piston moves.

Extremely close tolerances must be maintained if there is to be any hopeof the retention of pressure while permitting movement when necessary.Piston type separators also introduce an undesirable complication intothe arrangement of other parts where space problems are important. Thepresent invention overcomes these difliculties of prior art by utilizinga bladder of neoprene or the equivalent, stored in a compartmentseparated and sealed from the propellant by a diaphragm capable'ofwithstanding the normal storage pressure of about 50 p.s.i., but readilyrupturable at the timefor delivery of the propellant. The rupture of thediaphragm is accomplished by forcing a gas, such as nitrogen, under highpressure into the bladder, inflating it until the diaphragm yields. Thebladder will then expand to completely fill the fuel storage tank. Therewill be direct contact of the ice Such freezing primarily occurs becauseof the practical difliculty in excluding water vapor from the valveparts when exposed to the atmosphere.

In the present invention, the discharge-controlling valve is built intothe tank so that its moving parts are within the sealed area, while thesolenoid coil and a part of the magnetic path are disposed externally ofthe tank and separately detachable therefrom. This arrangement insuresthat the moving parts of the valve will always be bathed in propellant,preventing freezing. It provides means for controlling the propellantflow from the tank, for shuttingoff the propellant flow and confiningthe propellant when the tank. is to be removed, and for replacement ofthe tank without the removal of the solenoid and the disconnection ofthe electrical leads.

The objects of the invention thus include making it possible to usesatisfactory bladder materials in conjunction with chemically activepropellant fluids.

Another object is to improve the construction of the fuel storage anddelivery system for airborne devices of the guided missile type.

' Another object is to make it possible to remove the tank underpressure without loss of the propellant confind therein.

These and other objects will be apparent from the detailed descriptionfollowing in connection with the drawings, in which:

Fig. l is alongitudinal sectional view of a fuel storage tank embodyingthis invention shown in position for retaining fuel therein; and

Fig. 2 is a similar section showing the relationship of theparts afterdelivery of the fuel has been accomplished.

In the drawings, Fig. 1 represents a longitudinal section of a fuelstorage tank and discharge valve assembly indicated generally as 1. Thetank 2, which is of generally cylindrical form, has a bladder-containingend portion 4, in which are disposed the means for expelling propellantfrom the tank, and a control valve and delivery section, generallyindicated as 5, which acts to retain the fuel within the tank until theproper discharge time. by the actuation of a seal piercing plungerassembly 6 associated with the valve and delivery section 5, through gaspressure supplied from a reaction chamber through conduit means to bedescribed hereafter. Assembly 6 is illustrated and described to show howit cooperates with the control valve 5 but forms no part of the presentinvention. Its immediate function is to pierce a seal,

to be described hereafter, closing oif the outlet end of the fueldelivery section.

Prior to the time when fuel delivery is required, the tank 2 is filledwith a propellant such as ethylene oxide, under a pressure whichnormally is expected to be of the order of 50 pounds per square inch.The filling is accomplished through a fuel entry fitting 7 connected bysuitable conduits and valves, to a conventional ethylene oxide supplysource. These conduits and valves, and the ethyleneoxide source, arenotshown, being conventional in nature. A cap 8 may then-be applied toretain the fuel in the tank. Tank 2 is of sufiicient strength towithstand relatively high pressures, well in excess of the expulsionpressure of 840 p.s.i., which will be applied thereto at delivery time.The' end portion 4 has an annular body 10, with an integrally formedinwardly extending annular shoulder portion 11, presented to the tank 2,and

has seated thereagainst a metallic diaphragm 12. Annu Patented Apr.18,1961

At the desired time,'fuel delivery is permitted shoulder portion 11 byan annular bladder retaining member 16, held within body it) by meanssuch as a snap ring 17. An O-ring' 13 may be seated about thecircumference of retaining member 16 in order to assist in maintaining atight closure between the latter and the annular body member 16 duringthe initial stages of cx-, pulsion of the fuel from the tank. Diaphragm12 may be formed of brass of the order of .040 inch in thickness for thepresent pressures, necked down annularly to .010 inch adjacent to theinner periphery of shoulder 11. Alternatively, a two-part diaphragm, notshown, might be used. Such construction might involve a backing plateof.940 inch thickness to withstand the vapor pressure of the fuel, helddirectly by the retaining member 16, and of slightly lesser diameterthan the inwardly extending shoulder portion 11. The backing plate wouldhave fixed thereto a metallic diaphragm of .010 inch thickness and ofdiameter substantially equal to that of the retaining member 16.Pressure against the backing plate would then result in a peripheralshearing of the thin diaphragm facing the tank 2. Within retainingmember 16 is disposed a neoprene bladder 19, normally folded inaccordion pleated fashion, and arranged to receive an inert gas, such asnitrogen, under pressure. The nitrogen may be forced in at the time forfuel delivery through a supply pipe 26 and connecting boss 21 fixedcentrally through the end of retaining member 16, which may convenientlybe coaxially of the tank 2.. A nitrogen supply pressure of 840 psi. hasbeen found satisfactory.

The introduction of pressure in the bladder 19 will not, of itself,produce a discharge of the ethylene oxide, since the latter is retainedby the control valve assembly 5, which includes a sealing diaphragm 22.When the latter has been punctured by the piercing spear, however, thefuel may flow readily to the reaction chamber, and the valve assemblyopened.

The control valve assembly 5 is arranged to seal the tank 2 when notopened by the energization of solenoid means. It comprises an annularflanged mounting base 25 of high magnetic permeability suitably securedto the end of tank 2 opposite the end portion 4. The flanged mountingbase 25 is secured in position by means such as welding. A center plug26, also of high permability material, is connected threadably with boththe tank and the flanged mounting base 25. Plug 26 has formedtherethrough a discharge bore 27, to which entry of undfiired materialfrom tank 2 is protected by a curved filter screen 28. A plurality ofradially extending ribs 29, which may be formed separately of the tank2, or integrally therewith, are provided adjacent filter screen 28 toprevent the diaphragm 12 from covering enough of the screen to impedeflow of the liquid fuel through the discharge bore 27. The dischargebore 27 is coaxial with a valve bore or cylinder 30, of substantiallygreater diameter, formed within a body portion 31 formed integrally withthe base 25 and extending away from the tank 2. A piston type valvemember 32 is slidably disposed within valve cylinder 39. Valve member 32has an axial bore 33 formed therethrough which acts as a dischargepassage when the valve is in open position and cooperates with a springseat bore portion 34 formed in plug member 26, to act as a guide for ahelical spring 35. Spring 35 is thus seated within and in compressionagainst the screw plug 26 at one end, and against the valve member 32.at its other end. Axial bore 33 communicates with a plurality of outletbores 36 formed symmetrically and divergently from bore 33 about theaxis of the piston valve member 32. Centrally of the outlet bores 36, aconical valve portion 37 extends from valve member 32. Conical valveportion 37 is adapted to engage seatingly against a lesser diameterdischarge bore portion 39 formed coaxially within body portion 31 inextension of valve cylinder 30. Thus, spring 35 will normally holdconical valve portion 37 closed seatingly against the tion of themagnetic circuit. Body portion 31 has fitted therearound near dischargebore 39 an O-ring 42 which effects a slidable seal with a cylindricalsleeve portion 44 of an associated seal piercing assembly 6. Assembly 6opens seal 22 at the proper time, and a portion of the structurecooperates with the magnetic circuit which operates valve 32. Thedischarge terminal portion 45 of i the body portion 31 is threaded toreceive a centrally apertured screw collar 46, the function of which isto secure in place, the sealing diaphragm 22, which is the final closureelement for tank 2. Any fuel which leaks past the conical valve 37 willbe captured and retained by the sealing diaphragm 22.

The seal 22' is thus effective until it is penetrated by the sealpiercing assembly 6 at the desired delivery time. The seal piercingassembly 6 includes a cylindrical body member of high permeabilitymaterial formed integrally with the cylindrical sleeve portion 44,referred to above. Sleeve portion 44 fits snugly about the dischargeterminal portion 45 of the body portion 31 and within solenoid windings52, which, in turn, are snugly fitted about the body member 31. Solenoidwindings 52 are surrounded by an outer casing 53 of hi h permeabilitymaterial which surrounds the other magnetic circuit elements. Thecomplete magnetic circuit about solenoid windings 52 is shaped by theuse of high permeability magnetic materials for flanged member 25, plug26, piston 32, sleeve portion 44 and the outer casing 53, to follow amain flux field pattern, as indicated by the line 48 in Fig. 1. Thispath is such as to create a large traversing force on piston valve 32when the solenoid 52 is energized.

The seal piercing assembly 6 includes a cylinder bore 54 in which isslidably disposed a piston 55 having peripheral sealing means 56, suchas an G-ring, thereabout. A piston rod 57 disposed coaxially within thecylinder bore 54 and a piston rod bore 58 bears,at the end thereofentrance to bore 39, unless itis forcedopenby energizaopposite piston55, a piercing spear 59 having a central discharge bore 69 communicatingwith a transverse bore 61. Pressure is applied to piston 55 through aconduit 62 from a reaction chamber, not shown, at an appropriate time.When the piston 55 has been forced by such pres sure toward the tank 2into the pistion shown in Fig. 2, spear 59 pierces the diaphragm 22. Avent hole 63 is provided in the cylinder bore 54 in order to eliminateany gaseous pressure resistance within the cylinder to movement of thepiston 55. If the valve 37 is open, an outlet passage is availablethrough the discharge bores 60 and 61 of the spear, and an annularchamber 64% formed Within assembly 6, and communicating by means of afuel conduit 65, to the reaction chamber, not shown.

The solenoid windings 52 are energized by current supplied throughsolenoid leads 66, simultaneously with the creation of a high pressurewithin a reaction chamber which will be communicated through the conduit62 to the piston 55, and which will also be simultaneously actuated withan arrangement, not shown, for delivering nitrogen under pressurethrough the supply conduit 24). This actuating system, and the propertiming thereof, forms the subject matter'of my co -pending application,Fuel Supply System, Serial No. 679,796, filing date August 19, 1957, andonly so much is described herein as is necessary to an understanding ofthe present invention. When solenoid 52 is energized, the piston valve32 is forced open against the pressure of the spring 35. This withdrawsthe conical valve portion 37 from its seating contact with bore 39, andopens the fuel passage toward the diaphragm 22.

Simultaneously with the energization of solenoid 52, the pressure hasbeen set up in conduit 62, forcing the piston 55 to travel to theposition as shown in Fig. 2, penetrating the diaphragm and permittingthe fuel to con-- tinue its flow through chamber 64 and conduit 65 tothe reaction chamber, not shown, where it will be utilized. 'l heconduit' 62,: through which pressure is supplied-is formed through anend closure plate 67 suitably secured to the assembly 6 and sealedrelative to the cylinder bore 54 by means such as an O-ring 68.

The construction of the solenoid 52 and the assembly 5 is such that themagnetic flux lines tend to pass through the forwardly extending annularportion 44 of the assembly 6 and thence through the piston 32, returningthrough the flanged mounting base 25 to the outer shell 69 of thesolenoid. These parts are all formed of high permeability magneticmaterial, while the body portion 31 is formed of low permeabilitymagnetic material. This arrangement causes a concentration of the fiuXlines such that movement of the piston will be produced, withaccompanying release of the valve portion 37, when the coil isenergized.

It will be seen that with this arrangement, the tank 2 may bedisconnected from the entire assembly 6 and from the solenoid 52 at anytime prior to the piercing of the diaphragm 22, without releasing fuelfrom the tank 2 through valve 37 and outlet 39.

As soon, however, as the seal 22 is pierced, the nitrogen or otherpressurizing gas supplied to tank 2 at pressures of the order of 840psi. is able to expand the bladder 19 into every portion of the tank 2,forcing the propellant out through conduit 65 to the reaction chamberfor utilization.

It will be thus seen that there has been provided a simple mechanism forretaining a type of fuel tending to corrode flexible materials, in astorage tank without danger of affecting deleteriously a propulsionmember designed to force the fuel into an engine for consumption at adesired time.

The valve arrangement described permits the disconnection and removal ofthe tank from seal piercing means and from the solenoid coils used tocontrol the discharge valve without a loss of pressure from the tank. Atthe same time, the mechanism described is so simple in nature thatrelatively few moving parts are used and the outlet valve assemblyitself is not subject to disability through 6 freezing, since all of themoving parts may be continuously surrounded by the propellant fuel.

, What is claimed is:

In a fuel supply system, means for storing fuel under pressure whilepermitting delivery at a'prescribed time, comprising: a fuel storagetank; a propulsion bag compartment formed in a portion of said tank; arupturable diaphragm sealing said bag compartment from the remainder ofsaid storage tank; an inflatable bag of resilient, impermeable materialdisposed in said compartment; means for supplying propelling gas, of theclass of nitrogen, under pressure to said inflatable bagymeans forsupplying liquid fuel, of the class of ethylene oxide under pressure tosaid tank; a fuel delivery bore formed in said tank opposite said bagcompartment; a strainer element disposed about said fuel delivery bore;a piston valve slidably disposed within said fuel delivery bore andhaving a central openingrtherethrough adapted to receive spring meansfor positioning said piston valve, said piston valve being adapted toclose said delivery bore in one position and to permit the passage ofsaid liquid fuel in other positions; resilient means for normallymaintaining said piston valve in a position substantially to preventegress of said fuel; and

' another rupturable diaphagram positioned downstream from said pistonvalve for sealing said fuel delivery bore to prevent loss of materialleaking past said valve means, said last mentioned diaphragm being ofsufiicient strength to withstand maximum pressure of said fuel passingthrough said piston valve.

References Cited in the file of this patent UNITED STATES PATENTS2,402,826 Lubbock June 25, 1946 2,542,929 Kimball Feb. 10, 19512,546,325 Wasserlein Mar. 27, 1951 2,822,667 Drexel Feb. 11, 19582,859,808 Youngquist et al. Nov. 11, 1958

